"You wouldn't ask whether every hurricane has a center," the scientist replied, "if you knew a little more about them. As there is nothing for us to do but wait, and as it is foolish to go to the hurricane wing until the time of danger, I might as well explain to you what a hurricane really is. Then, if you live through it----" Stuart jumped at the sudden idea of the imminent danger--"you'll be able to write to your paper about it, intelligently." "I'd really like to know," declared Stuart, leaning forward eagerly. "Well," said his informant, "I'll make it as simple as I can, though, I warn you, a hurricane isn't a subject that can be explained in a sentence or two. "You know that summer and winter weather are different. You ought to be able to see that summer and winter winds are different. The difference in seasons is caused by the respective positions of the northern and southern hemispheres to the sun. The greater the heat, the greater the atmospheric changes. Hurricanes are great whirls caused by violent changes of the air. Therefore hurricanes come only in the summer." "That's clear and easy!" declared the boy, delighted that he was able to follow the explanation. "Now, as to why hurricanes strike here and nowhere else. I'll try and explain that, too. There is a belt of ocean, just north of and on the equator, known as the 'doldrums,' where it is nearly always calm, and very hot. There is also a belt of air running from Southern Europe to the West Indies where the north-east trade winds blow all the year round. Between this perpetual calm of the doldrums and the perpetual wind of the trades is a region of atmospheric instability. "Now, consider conditions to the west of us. The Caribbean Sea and the Gulf of Mexico, together, form what is almost a great inland sea with the West Indian Islands as its eastern shore. The trade winds do not reach it. The Pacific winds do not reach it, for they are diverted by the high ranges of Central America. The winds from North America do not reach it, because these always turn northwards on reaching the Mississippi Valley and leave the United States by the St. Lawrence Valley. "So, Stuart, you can see that the Caribbean Sea and the Gulf of Mexico have over them, in summer, a region of air, little disturbed by wind, not far from the Equator and which, therefore, becomes steadily heated and steadily saturated by the evaporation from the body of water below." "Yes," agreed the boy, "I can see that." "Very good. Now, such a steady heating of one section of air is bound to disturb the balance of the atmosphere. This disturbance, moreover, must be acted upon by the rotation of the earth. Just as all the weather in the United States comes from the west and travels eastwards, so the track of hurricane origins travels eastwards during the course of a summer.